The semiconductor industry is continuously moving toward the fabrication of smaller and more complex microelectronic components with higher performance. The production of smaller integrated circuits requires the development of smaller electronic components, and closer spacing of those electronic components within the integrated circuits. Circuit designs that reduce the number of components used for a required function can reduce circuit component crowding.
Many integrated circuits include a plurality of common lines (including ground lines), and these common lines are typically electrically connected together with protective electrostatic discharge lines. Theses electrostatic discharge lines (ESD lines) are often provided in pairs, where one ESD line is configured for current flow in one direction between a pair of common lines, and the other mated ESD line is configured for current flow in the opposite direction. Diodes are typically used to configure an ESD line for a desired direction of flow, where a diode allows current to flow in one direction but not in the other.
The electrical connection of different common lines can lead to current leakage from one common line to another, where this current leakage is commonly referred to as “noise.” Noise is typically produced by a voltage spike in one common line that results in current being transferred to another common line. Noise can be limited by establishing a discharge voltage for the ESD line, where current is not transferred through the ESD line if the voltage drop between the common lines is less than the discharge voltage, but current is allowed to flow if the voltage drop is greater than the discharge voltage. Typically, a preset voltage is required for a single diode to allow current flow, so when a discharge voltage that is higher than the preset voltage is desired, a plurality of diodes are positioned in series. The preset voltage is typically about 0.5 volts for many types of diodes used in the ESD lines. Therefore, if the desired discharge voltage is 4 time higher than the preset voltage, 4 diodes are connected in series in each of the two mated ESD lines. If the desired discharge voltage is 8 times higher than the preset voltage, then 8 diodes are included in each of the two mated ESD lines. Forming ESD lines with several diodes uses valuable space in an integrated circuit, and extra components provide more opportunities for failure.
Accordingly, it is desirable to provide integrated circuits with ESD lines that have fewer components than an ESD line with multiple diodes, and methods of producing the same. In addition, it is desirable to provide integrated circuits with ESD lines where the discharge voltage can be set at a wide variety of values without requiring additional diodes for higher discharge voltages. Furthermore, other desirable features and characteristics of the present embodiment will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.